This invention relates generally to disposable filters, and more particularly concerns nonwoven, secondary disposable filters for use with the standard metal filters found on conventional stove hoods.
Stoves and cooking ranges are frequently provided with exhaust hoods including a fan which draws the cooking fumes from the area above the cooking surface, filters out grease and smoke particles, and exhausts the filtered fumes either outside of the dwelling or back into the room. If the cooking oils and greases are not filtered out of the air, they will deposit on the surfaces of the hood, the exhaust fan, and the ducts leading to outside the dwelling. Over time, such layer of grease is not only source of objectional odors and filth, but it also represents a fire hazard.
Conventionally, the filters used on stove hoods have been formed of aluminum or other expanded metal mesh. Such filters rely totally on the impaction of oil and grease particles on the surface of the metal lattice which has pore sizes of approximately 1/8 of an inch. Because such metal lattic filters are reasonably expensive, they are intended to be cleaned and reused and not simply thrown away. Cleaning accumulated grease and oil from the surface of such metal filters is both a time consuming and unpleasant task which requires soaking the filter in a suitable cleaning agent to loosen and dissolve the accumulated grease.
In addition, for those stove hoods which filter the fumes and exhaust the filtered air back into the room, such metal filters, which rely solely on impaction, cannot move the smaller smoke particulate which may be part of the cooking fumes.
Dargel U.S. Pat. No. 4,518,402 discloses a reusable air filter system for air conditioners, furnaces, and grease hoods. The filter element consists of fine mesh polypropylene in the form of sheets. Two sheets, preferably 12 mils in thickness, are provided at the upstream side and the downstream side of the filter element. Between the two upstream side sheets and the two downstream side sheets lies a three-dimensional layer of polypropylene which is 20 mils in thickness and which folds over on itself to form a generally U-shaped filtering stage with a gap therebetween. The polypropylene sheets are permanently fitted within a metal frame and protected by a metal grating. The filter system is cleanable and reusable.
Terrel et al. U.S. Pat. No. 3,854,912 discloses a self-contained unitary filter element including both a grease trap type air filter and an air cleansing or purifying filter. The grease trap member is a dished receptacle constructed of a plurality of metal layers such as expanded aluminum which provide a tortuous path through the various layers, thereby trapping the grease by impaction. The air cleansing filter consists of loose particulate charcoal granules simply poured into the dish-shaped grease trap. Alternatively, a bag-like cover may be used to enclose the charcoal granules when placed within the dish-shaped grease filter.
Arons et al. U.S. Pat. No. 4,217,386 discloses laminated fabric including activated carbon fabric for cleansing air of toxic chemical vapors. The laminate is formed of consecutive layers of spun-bond polyolefin material, melt-blown polyolefin materials, a woven active carbon fabric, melt-blown polyolefin material, and spun-bond polyolefin material. The spun-bond and melt-blown materials are laminated together and have a combined basis weight of 1.5 oz./yd.sup.2.
Sherwood U.S. Pat. No. 4,540,625 discloses a polypropylene fabric formed by a process involving the cooling and agitation of the polymer solution while subjecting the solution to the application of sonic vibrations. The resulting polypropylene fabric is impregnated with solid particles of activated charcoal positioned within the intersticial spaces between the nonwoven fabric.
Boylan U.S. Pat. No. 3,127,259 discloses a frame to which a filter element may be attached and detached by means of a zipper, tape, or Velcro tape.
The prior art thus does not provide a nonwoven, disposable secondary filter which is easily attachable and detachable from the primary metal lattice filter of a stove hood.